1. Field of the Invention
The present invention relates to a pest animal repulsing apparatus which utilizes ultrasonic waves that are generated randomly to intimidate and repulse pest animals such as rats and to prevent them from entering a designated area such as a residential building, supermarket, department store or the like.
2. Description of the Related Art
In view of the fact that pest animals such as rats dislike ultrasonic waves within a specific range, apparatuses in the known art that repulse rats and the like by emitting ultrasonic waves toward the area where the rats and the like live are disclosed, for instance, in Japanese Examined Patent Publication No. S 61-49 and Japanese Examined Patent Publication No. S 63-16.
The apparatus that is disclosed in the former publication, i.e., Japanese Examined Patent Publication No. S 61-49, creates a control signal by superimposing a trigger signal generated at a trigger signal generator upon a random signal generated at a random signal generator and provides this control signal to an oscillating circuit to cause random changes in the oscillating frequency. An intimidating signal is thereby formed that contains an impulsive sound component whereby changes in frequency such that a rapid change from a reduction to an increase in frequency occurs within this randomly generated oscillating frequency. The intimidating signal is changed by a transducer to ultrasonic waves that contain impulsive sound.
In addition, in the apparatus disclosed in the latter publication, i.e., Japanese Examined Patent Publication No. S63-16, in which the trigger signal in the apparatus disclosed in the former publication is eliminated, a control signal corresponding to the output of a random signal generator is provided to an oscillating circuit to cause random changes in the oscillating frequency. An intimidating signal is thereby formed that contains an impulsive sound component whereby rapid changes from a reduction to an increase in frequency occur within this randomly generated oscillating frequency and the intimidating signal is changed to ultrasonic waves that contain impulsive sound by a transducer.
However, with the apparatuses described above, which intimidate rats and the like by simultaneously generating random ultrasonic waves and impulse waves, if such apparatuses are to cover a wide range of area, a plurality of transducers must be connected to the oscillating circuit via the amplifying circuits, and this may present a problem of an insufficient source capacity. Thus, a wide ranging area cannot be covered unless the source capacity of the apparatus is increased so as to make it possible to increase the number of transducers which can be connected.
In addition, while the applicant of the present invention has been conducting research into a method in which output systems for ultrasonic waves are switched in order to prevent rats and the like from becoming accustomed to the ultrasonic waves, there is a problem in that, when the output systems for the ultrasonic waves that are outputted continuously are switched, noise is generated at the transducers when switching the output systems.